1、BRITISH STANDARD BS EN 12789:2002 Advanced technical ceramics Mechanical properties of ceramic composites at high temperature under air at atmospheric pressure Determination of flexural strength The European Standard EN 12789:2002 has the status of a British Standard ICS 81.060.30 BS EN 12789:2002 T
2、his British Standard was published under the authority of the Standards Policy and Strategy Committee on 17 April 2003 BSI 17 April 2003 ISBN 0 580 41587 2 National foreword This British Standard is the official English language version of EN 12789:2002. It supersedes DD ENV 12789:1998 which is with
3、drawn. The UK participation in its preparation was entrusted to Technical Committee RPI/13, Advanced technical ceramics, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which im
4、plement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication
5、does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/Euro
6、pean committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pa
7、ges 2 to 13 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN12789 October2002 ICS81.060.30 SupersedesENV12789:1998 Englishversio
8、n AdvancedtechnicalceramicsMechanicalpropertiesofceramic compositesathightemperatureunderairatatmospheric pressureDeterminationofflexuralstrength CramiquestechniquesavancesPropritsmcaniques descramiquescompositeshautetempraturesousair pressionatmosphriqueDterminationdelarsistance enflexion Hochleist
9、ungskeramikMechanischeEigenschaftenvon keramischenVerbundwerkstoffenbeihoherTemperaturau LuftbeiAtmosphrendruckBestimmunngder Beigefestigkeit ThisEuropeanStandardwasapprovedbyCENon7September2002. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisE
10、urope an Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheManagementCentreortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlang
11、uagemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheManagementCentrehasthesamestatusasthe official versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,CzechRepublic,Denmark,Finland,France,Germany,Greece, Iceland,Ireland,Italy,Luxembourg,Malta,Net
12、herlands,Norway,Portugal,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2002CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers.
13、Ref.No.EN12789:2002EEN12789:2002(E) 2 Contents page Foreword3 1 Scope 4 2 Normativereferences 4 3 Principle4 4 Termsanddefinitions. .4 5 Apparatus .5 5.1 Testmachine 5 5.2 Testjig .5 5.3 Setupforheating 5 5.4 Temperaturemeasurement. 6 5.5 Datarecordingsystem . .6 5.6 Micrometers6 6 Testpieces. .6 7
14、Testpiecepreparation .7 7.1 Machiningandpreparation. 7 7.2 Numberoftestpieces . 7 8 Testprocedures . 7 8.1 Testsetup:temperatureconsiderations . .7 8.2 Testsetup:otherconsiderations. .8 8.3 Testingtechnique . .8 8.4 Testvalidity . .9 9 Calculationofresults 9 9.1 Testpieceorigin. 9 9.2 Flexuralstreng
15、th. .9 10 Testreport 11 Bibliography 13EN12789:2002(E) 3 Foreword Thisdocument(EN12789:2002)hasbeenpreparedbyTechnicalCommitteeCEN/TC184“Advancedtechnical ceramics“,thesecretariatofwhichisheldbyBSI. ThisEuropeanStandardshallbegiventhestatusofanationalstandard,eitherbypublicationofanidenticaltextor b
16、yendorsement,atthelatestbyApril2003,andconflictingnationalstandardsshallbewithdrawnatthelatestby April2003. ThisdocumentsupersedesENV12789:1998. AccordingtotheCEN/CENELECInternalRegulations,thenationalstandardsorganizationsofthefollowing countriesareboundtoimplementthisEuropeanStandard:Austria,Belgi
17、um,CzechRepublic,Denmark,Finland, France,Germany,Greece,Iceland,Ireland,Italy,Luxembourg,Malta,Netherlands,Norway,Portugal,Spain, Sweden,SwitzerlandandtheUnitedKingdom.EN12789:2002(E) 4 1Scope ThisEuropeanStandardspecifiestheconditionsfordeterminationoftheflexuralstrengthofceramicmatrix compositemat
18、erialswithcontinuousfibrereinforcementunderthreepointorfourpointbendingfortemperatures upto1700Cinairatatmosphericpressure. Thisstandardappliestoallceramicmatrixcompositeswithacontinuousfibrereinforcement,unidirectional(1D), bidirectional(2D),andtridirectional(xD,with2x3),loadedalongoneprincipalaxis
19、ofreinforcement. NOTE1 Inmostcases,ceramicmatrixcompositestobeusedathightemperatureinairarecoatedwithanantioxidation coating. NOTE2 Thepurposeofthisstandardistodeterminetheflexuralstrengthofamaterialunderanoxidizingenvironmentbut nottomeasurematerialoxidation. 2 Normativereferences ThisEuropeanStand
20、ardincorporatesbydatedorundatedreference,provisionsfromotherpublications.These normativereferencesarecitedattheappropriateplacesinthetext,andthepublicationsarelistedhereafter.For datedreferences,subsequentamendmentstoorrevisionsofanyofthesepublicationsapplytothisEuropean Standardonlywhenincorporated
21、initbyamendmentorrevision.Forundatedreferencesthelatesteditionofthe publicationreferredtoapplies(includingamendments). ENISO75001, MetallicmaterialsVerificationofstaticuniaxialtestingmachinesPart1:Tension/compression testingmachines(ISO75001:1999) . EN605841, ThermocouplesPart1:Referencetables.(IEC6
22、05841:1995) . EN605842, ThermocouplesPart2:Tolerances .(IEC605842:1982+A1:1989) . ISO3611, Micrometercallipersforexternalmeasurement. 3Principle Atestpieceofspecifieddimensionsisheatedtothetestingtemperature.Itissubsequentlyloadedinflexureto fractureinsuchawaythatfailureoccursintensionorincompressio
23、nalongoneprincipalaxisofreinforcement. Thetestisperformedatconstantcrossheaddisplacementrate. Thetestdurationislimitedtoreduceanytimedependenteffects(creep,etc.). 4 Termsanddefinitions ForthepurposesofthisEuropeanStandard,thefollowingtermsanddefinitionsapply. 4.1 testtemperature, T temperatureatthec
24、entreofthetestpiece 4.2 maximumflexuralforce, F m highestrecordedforceinaflexuraltestonthetestpiecewhentestedtofailureEN12789:2002(E) 5 4.3 flexuralstress, ss thenominalstressontheoutersurfaceofthetestpiece,calculatedatmidspan NOTE Thisstressisconventionallycalculatedaccordingtothesimplebeamtheory,w
25、hosebasicassumptionscannotbe metbyceramicmatrixcompositematerials. 4.4 flexuralstrength, ss f,m maximumflexuralstressappliedtoatestpiecethatfracturesduringaflexuraltest twoflexuralstrengthscanbedistinguished: apparentflexuralstrength, s f,m,a ,whentheapparentdimensionsareused effectiveflexuralstreng
26、th, s f,m,e ,whenthedimensionsarecorrectedbyafactortoaccountforthepresence oftheantioxidativeprotection 5Apparatus 5.1 Testmachine Themachineshallbeequippedwithasystemformeasuringtheforceappliedtothetestpiece.Thesystemshall conformtograde1accordingtoENISO75001. 5.2 Testjig Thetestjigiscomposedoftwop
27、arts,linkedtothefixedandmobilepartsofthemachine.Ithastwooutersupport rollersandone(threepointbending)ortwo(fourpointbending)innersupportrollers. Thematerialofthejigandthatoftherollersshallnotreactwiththatofthespecimen,norwiththeenvironment. Thecylindricalrollersshallhaveadiameterof4mmto10mm.Theirlen
28、gthshallbeatleastequaltothewidthof thespecimen.Theyshallbemadeofamaterialwithahardnessatleastequaltothatofthespecimen.Theaxesof therollersshallbeparalleltowithin0,01mm/mm. Theouterrollers(threeandfourpointbending)andinnerrollers(fourpointbending)shallbefreetorotate(see Figure1). Eithertwoorthreeroll
29、ers,forthreepointorfourpointbendingrespectively,shallbefreetopivotaroundanaxis paralleltothelongitudinaldirectionofthetestpiece,inordertoadapttothenonparallelismoftheupperandlower facesofunmachinedtestpieces(seeFigure1). Therollingandpivotingabilityoftherollersshallnotbeaffectedbyheating.Thedistance
30、betweenrollersshallbe inaccordancetoclause6. Theinnerroller(s)shallbecentredwithrespecttotheouterrollerstowithin0,2mm.Inthecaseoffourpoint bendingalevellingsystemshallbeusedtoensuresymmetricalloadingofthetestpiece. Theperformanceshallnotchangebecauseofheating. 5.3 Setupforheating Thesetupforheatings
31、hallbeconstructedinsuchawaythatthevariationoftemperatureofpartofthetestpiece whichisbetweentheoutersupportrollersislessthan50Cattesttemperature.EN12789:2002(E) 6 5.4Temperature measurement ThermocouplesshallcomplywithEN605841andEN605842.Alternatively,pyrometersorthermocoupleswhich arenotcoveredbyEN6
32、05841andEN605842,butwhichareappropriatelycalibratedcanbeused. 5.5 Datarecordingsystem Acalibratedrecordershallbeusedtorecordforcetimecurve.Theuseofadigitaldatarecordingsystemcombined withananaloguerecorderisrecommended. 5.6Micrometers Micrometersusedforthemeasurementofthedimensionsofthetestpieceshal
33、lbeinaccordancewithISO3611. 6 Testpieces RecommendedspecimendimensionsaregiveninTable1.Thesedimensionshavebeensuccessfullyusedand takedueaccountofthefollowingfactors: Theamountofmaterialunderloadshallberepresentativeofthenatureofthematerialandofthereinforcement structure.Thissetsminimumlimitstothesp
34、anandtothewidthandthicknessofthespecimen.Inthecaseof flexural,asopposedtotensiletesting,alsothedistributionofthelongitudinalreinforcementthroughthethickness hastobeconsidered.Whenthisdistributionisnotsymmetricalwithrespecttotheneutralplane,careshallbe takentoinsurethatitissimilarbetweenspecimens. Th
35、ethicknessandthedistancebetweentheinnerandouterroller(s)shallbechosensoastoavoidshearfailure. Thisisachievedbysettingaminimumlimittotheratiobetweenthemomentarmandthespecimenthickness.A valueof10iscommonlyusedandtranslatesintoaminimumL/hratioof20inthreepointbending,andaminimum (LLi)/hratioof20infourp
36、ointbendingwithLi=L/3. Otherfactorsaffectingthesizeanddimensionsofthespecimensarethetypeoftheheatingandoftheloading system. Table1Recommendedtestspecimenandspandimensions Dimensionsinmillimetres 1D,2D&xD Tolerance L t ,totallength L+10 +1 b,width 10 +0,2 h,thickness 2,5 +0,2 Innerspan fourpointbendi
37、ng,L i 25 +0,1 Outerspan fourpointbending,L 75 +0,1 threepointbending,L 50 +0,1 NOTE Ifitisnecessarytodefinetestpiecesofdifferentdimensions,theconditionsofclause6shouldbetakeninto account.EN12789:2002(E) 7 7 Testpiecepreparation 7.1 Machiningandpreparation Duringcuttingout,careshallbetakentoalignthe
38、longitudinaltestpieceaxiswithoneoftheprincipalaxesof reinforcement. Specimensmaybetestedwitheithermachinedornonmachinedtopandbottomsurfaces.Insomecases machiningisnotrecommendedbecauseitmaycausebreakageofthefibresnearthetopandbottomsurfacesas wellasdamagetotheantioxidationcoatingifpresent.Whenmachin
39、ingthesesurfaces,careshallbetakento maintainareinforcementgeometryacrossthethicknessofthespecimen,whichisrepresentativeofthematerialin theasprocessedcondition.Inparticular,itshallbeassuredthatthesymmetryofanoriginallysymmetric reinforcementgeometryispreservedinthespecimencrosssectionaftermachining.
40、Machiningparameterswhichavoiddamagetothematerialshallbeestablishedanddocumented.These parametersshallbeadheredtoduringtestpiecepreparation. NOTE Whenspecimensaremachinedfromaplatewhichhasbeenprotectedagainstoxidation,thecutsurfacesofthe specimenareunprotected.Thesesurfacesshouldbeprotectedtoprevento
41、xidation. 7.2 Numberoftestpieces Atleastfivevalidtestresults,asspecifiedinparagraph8.4arerequiredperloadingcondition.Forspecimenswith anonsymmetricreinforcementgeometrywithrespecttotheneutralplane,testsintwoorientationsforwhichthe tensileandcompressivefaceareinterchangedmaybenecessary. Ifastatistica
42、levaluationoftheflexuralstrengthisrequired,thenumberoftestpiecesshallbeinaccordancewith ENV8435. 8 Testprocedures 8.1 Testsetup:temperatureconsiderations Thefollowingdeterminationshallbecarriedoutunderconditionsrepresentativeofthetests,andshallberepeated everytimethereisachangeinmaterial,inspecimeng
43、eometry,inloadingattachments,etc.Inestablishingthem, timeshallbeallowedfortemperaturestabilisation. Priortotesting,thetemperaturegradientwithintheouterspanshallbeestablishedoverthetemperaturerangeof interest.Thisshallbedonebymeasuringthespecimentemperatureataminimumofthreelocations,whichshall bethepointsoverthesupportsandatthecentre.Thetemperaturevariationwithintheouterspanshallmeetthe requirementsofparagraph5.3. Duringaseriesoftests,thetesttemperaturecanbedeterminedeitherdirectlyby
